This invention generally relates to medical instruments such as retrieval devices for retrieving material from within a body. More particularly, the invention relates to retrieval devices for capturing and releasing stones such as urinary tract stones, gall stones, and other biological materials from a body tract.
Medical retrieval devices generally are used to retrieve biological and foreign material including stones from the body. Such medical retrieval devices may be used through an endoscope or a laparoscope.
One type of known medical retrieval device has a sheath and a retrieval assembly such as a basket that is movable in and out of the sheath. When the basket is within the sheath, the basket assumes a collapsed, reduced diameter profile. When the sheath is retracted relative to the basket or the basket is moved beyond the end of the sheath, the basket expands to a relatively larger diameter than when the basket is enclosed within the sheath. Generally, the contour of known baskets is round or oval and is formed by a plurality of legs.
With many known retrieval devices, materials are used in the retrieval assembly to enhance its rigidity. However, rigid materials used to enhance strength do so at the expense of flexibility. The retrieval assembly must, on the one hand, be sufficiently strong to dilate the body tract and, on the other hand, be sufficiently flexible to negotiate body tracts having small diameters, tortuous pathways and irregular lumens. Moreover, flexible retrieval assemblies can more easily capture large stones through the gaps in the legs of the retrieval assembly, than can rigid retrieval assemblies. When flexible materials are used in the retrieval assembly, however, rigidity and strength are compromised.
It is an object of the invention to provide a medical instrument, i.e., a medical retrieval device with features that permit retrieval of material within a body. The material can be biological material, such as stones, or foreign material, or any of a variety of other types of material within a body. The material can be located in a urinary or biliary tract or elsewhere in the body.
A medical instrument according to the invention is used to treat an internal organ which includes material such as a calculus or a thromboembolus. The medical instrument typically includes a proximal handle, a sheath extending from the handle and including a lumen and a distal end away from the handle, and a retrieval assembly such as a basket. The retrieval assembly has a proximal portion and a distal portion. The proximal portion is made with a first material and the distal portion is made with a second different material.
The retrieval assembly and the sheath are moveable relative to each other to achieve a collapsed position of the retrieval assembly in which the retrieval assembly is within the lumen of the sheath and another position of the retrieval assembly in which at least a portion of the retrieval assembly extends from the distal end of the sheath. In this position, the retrieval assembly assumes a three-dimensional shape out of the lumen of the sheath.
In one embodiment, the retrieval assembly is a basket. The basket has a plurality of legs, for example, the basket has three, four, five or more legs. The legs may be preformed.
In one embodiment of the invention, the legs of the retrieval assembly feature a proximal and a distal portion. The proximal portion of the legs comprises a first material and the distal portion of the legs comprises a second material, the second material being more flexible than the first material. In this embodiment, the proximal leg portion and the distal leg portion are connected at ajoint. The joint is a loop, hook, crimp, solder, weld, or any other mechanism known for connecting the ends of at least two wires or legs.
In another embodiment of the medical retrieval device of the invention, the proximal portion of the retrieval assembly is generally straight; the contour of the proximal portion being planar rather than curved. Alternatively, at least the proximal portion of the retrieval assembly is bulbous, i.e., the proximal portion is bowed out from the center of the retrieval device when the proximal portion is deployed beyond the distal end of the sheath.
Other embodiments of this invention include a sheath axially moveable relative to the retrieval assembly. In this embodiment, retraction of the sheath in a direction away from the distal end of the sheath extends the retrieval assembly from the distal end of the sheath. The portions of the retrieval assembly are thereby expanded depending on which portions are uncovered by the retracted sheath.
Some additional embodiments of the invention include an elongated guide member longitudinally positioned in the lumen of the sheath, operably attached to a proximal end of the retrieval assembly, and actuated by at least one actuating member on the handle. Reciprocal axial movement of the elongated guide member moves the retrieval assembly from its enclosed position within the sheath, in and out of the distal end of the sheath and back to its enclosed position within the sheath. As the assembly is moved in and out the sheath, the portions of the retrieval assembly shift between collapsed and opened positions.
In yet another aspect, the invention relates to a method for retrieving material from a body. The method comprises inserting a medical retrieval device with a retrieval assembly (such as the instrument described above) into a body, extending the proximal and distal portions of the retrieval assembly beyond the end of the sheath, maneuvering the retrieval assembly around the material, capturing the material within the retrieval assembly, withdrawing the proximal and distal portions of the retrieval assembly back into the sheath, and removing the medical instrument and the material captured in the retrieval assembly from the body.